FDA warning letter treats compounded retatrutide as an unapproved new drug

The U.S. Food and Drug Administration issued a warning letter dated September 9, 2025, to GLP-1 Solution, a seller based in Berlin, Germany that operates the website glp1solution.store ^[1]. After reviewing the site in August 2025, the agency found that the company was offering compounded versions of three drugs sold under other conditions: retatrutide, semaglutide and tirzepatide ^[1].

The FDA says the compounded retatrutide products are "unapproved new drugs" and "misbranded drugs" under sections 505(a), 502(f)(1), 301(a) and 301(d) of the Federal Food, Drug, and Cosmetic Act ^[1]. Retatrutide is not the subject of an applicable United States Pharmacopeia or National Formulary monograph, is not a component of an FDA-approved human drug, and does not appear on the list of bulk substances that compounding pharmacies are allowed to use under section 503A ^[1]. It also does not appear on the separate list used by outsourcing facilities under section 503B, and it is not linked to any drug currently on the FDA's shortage list, which is the other pathway that can justify compounding with an otherwise restricted ingredient ^[1]. Because none of those conditions are met, the FDA says the retatrutide products cannot claim the exemptions that let compounders skip FDA approval and standard labeling requirements ^[1].

The letter separately addresses claims the company made about its compounded semaglutide and tirzepatide. The FDA quotes two examples from the website: the word "MOUNJARO" and a statement that "Semaglutide is the generic drug delivered in Ozempic (injectable) and Rybelsus (oral) diabetes control medications, and Wegovy (injectable) weight loss medication" ^[1]. The agency says these claims are false or misleading because they imply the compounded products are the same as FDA-approved brand-name drugs, when they are not ^[1]. That puts the products in violation of sections 502(a) and 502(bb) of the FDCA, which prohibit false or misleading labeling and advertising for compounded drugs ^[1].

Why it matters for patients

Retatrutide is not an FDA-approved medication under any brand name, and neither Ozempic, Wegovy, Rybelsus, Mounjaro nor any other approved GLP-1 product is legally interchangeable with a compounded version made outside the approved manufacturing and testing system ^[1]. The FDA's letter underscores that compounded drugs sold under names or descriptions that suggest equivalence to approved brands are not verified by the agency for safety, effectiveness or manufacturing quality in the same way ^[1]. Patients considering a compounded GLP-1 product from an online seller may not know whether the product they receive matches its labeling, since the FDA's action here was based on a review of website claims rather than laboratory testing of the products themselves ^[1].

What happens next

The warning letter, dated September 9, 2025, asks GLP-1 Solution to address the violations described, though the excerpt provided does not specify a response deadline or describe what enforcement steps might follow if the company does not comply ^[1]. The sources reviewed do not indicate whether the company has responded, whether its products remain for sale, or whether the FDA plans further action against this seller or others offering similar compounded retatrutide products ^[1]. Anyone tracking this case will need to watch for updates directly from the FDA's warning letter database, since no follow-up information is available in the material reviewed here.